1. Field of the Invention
The present invention relates to an inverter apparatus.
2. Description of the Related Art
When a break or a voltage sag occurs in an alternate-current power system (hereinafter, “system-voltage sag or the like”), a conventional inverter apparatus causes each of switching elements of an inverter to turn off, thereby avoiding any abnormal current passing through the switching elements. However, even when giving a stop command signal to each of the switching elements, if a power voltage of a control circuit that controls the switching elements decreases, sometimes the control circuit cannot maintain the stop command signal, and an abnormal switching command may be output to the switching elements in some cases. For example, if an abnormal switching command that establishes a short circuit in an inverter main circuit is output to each of the switching elements of the main circuit, there is a possibility that an overcurrent based on a charge stored in a capacitor for a direct-current power circuit may pass through the switching elements.
On the other hand, an inverter apparatus disclosed in Japanese Patent Application Laid-open No. H2-269479 is configured to give a stop command signal to switching elements upon an occurrence of a system-voltage sag or the like based on a detection signal about the event that is detected, and to cause a discharge circuit to discharge a charge in the capacitor after the switching elements are turned to a steady OFF-state, and operation of an inverter is stopped. Accordingly, even if the power voltage of the control circuit decreases and the control circuit can no longer maintain the stop command, the charge stored in the capacitor does not pass through the switching elements as an overcurrent.
However, in the inverter circuit described above, because the charge stored in the capacitor is discharged when a system-voltage sag or the like occurs, the capacitor needs to be recharged when restarting the inverter apparatus. Consequently, when restarting the inverter apparatus, there is a problem that a charging time is required for storing a predetermined charge in the capacitor.